Precision Frequency Marker
Cryptic letters are codes for Japanese/Chinese characters. English readers may skip them.

$B:G6a(B12.8MHz$B$N(BTCXO$B!J(B $B29EYJd=~7??e>=H/?64o(B $B!K$,%8%c%s%/20$5$s$J$I$G0B$/=P2s$C(B $B$F$$$^$9!JNc$($P=)7nEE;R$G0l8D(B200$B1_!K!#$=$NL>$NDL$j!"29EYJQ2=$KBP$7$F(B $B<~GH?t$,$H$F$b0BDj$K$J$k$h$&$K:n$i$l$F$*$j!"<~GH?t$OHyD4$G$-$k$h$&$K(B $B$J$C$F$$$^$9!#(B

$B2sO)?^$K$"$k$h$&$K!"(BTCXO$B$+$i$N(B12.8MHz$B$N%/%m%C%/$O(B74HC4060$B$H$$$&(B2$B?J%+%&(B $B%s%?$G(B1/128$BJ,<~$5$l$F(B100kHz$B$N%/%m%C%/$,:n$i$l$^$9!#$5$i$K(B1/2$B$5$l$F(B50kHz$B!"(B $B$5$i$K(B1/2$B$G(B25kHz$B$,:n$i$l$^$9!#$l(B 74HC4518$B$H$$$&(BBCD$B%+%&%s%?$G(B1/10$BJ,<~$5$l$F(B10kHz$B$H(B5kHz$B$,:n$i$l$^$9!#(B

$B:G=i$K(B100kHzmail protected]_Dj$7$F(BTCXO$B$r(BJJY$BEy$NI8=`EEGH$H%<%m%S!<%[email protected]$7(B $B$F$*$1$P!"<~GH?t$,D94|[email protected]$J<~GH?t%^!<%+!<$,$G$-$^$9!#Nc$($P!"(B100kHz $B$K%;%C%H$9$k$H

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Precision Frequency Marker

Recently, cheap TCXO modules with a frequency of 12.8MHz are on the surplus market(at least in Japan). TCXO stands for Temperature Compensated X'tal Oscillator. It is a fine-tunable oscillator module packed in a small can with an excellent frequency stability against ambient temperature change.

As you see in the schematic diagram, the 12.8MHz clock signal from the TCXO is divided by 128 with a binary counter 74HC4060 to make a 100kHz clock. Then, further divided by two and another two to make clock signals of 50kHz and 25kHz. The 100kHz and 50kHz clocks are again divided by ten with a BCD counter 74HC4518 to make clocks of 10kHz and 5kHz, respectively.

At first, select 100kHz and zero-in with the standard frequency of e.g. WWV by tuning the trim-pot of TCXO, then you have a self-maintained precision frequency marker for your homebrew rigs. If you select 100kHz clock for instance, then you hear the maker beat signals every 100kHz with your receiver.

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MINOWA, Makoto
7N3WVM
Last revised 1998-06-05.